The present invention relates to a printed antenna whose elements are capacitively coupled to feedlines. More specifically, the invention relates to a high aperture efficiency, high polarization purity antenna element is transparent to orthogonally polarized radiation. The invention is applicable to printed circuit antennas employing single-polarization and dual-polarization geometries.
Printed circuit antennas employing capacitive coupling are known. A single-polarization version of such an antenna is disclosed in U.S. application Ser. No. 748,637, filed June 25, 1985, now U.S. Pat. No. 4,761,654. In that application, the disclosure of which is incorporated herein by reference, both linear and circular polarization are achieved in an antenna which employs capacitive coupling between the feedlines the feeding elements, and also between the feeding elements radiating elements.
Copending application Ser. No. 930,187, filed Nov. 13, 1986, discloses an improvement on the techniques disclosed in the first-mentioned application. The contents of that application also are incorporated herein by reference.
A dual-polarized printed circuit antenna is disclosed in copending application Ser. No. 165,332, filed Mar. 8, 1988, entitled "Dual-Polarized Printed-Circuit Antenna Employing Patches or Slots Capacitively Coupled to Feedlines", the named inventors being Robert M. Sorbello, John E. Effland, and Amir I. Zaghloul. In the last-mentioned application, a technique is provided wherein two senses of polarization, orthogonal to each other, may be achieved with appropriate isolation between the arrays of radiating elements. That application also is incorporated herein by reference.
An example of the dual polarization geometry is shown in FIG. 1, in which elements 1a and 1b are shown in element arrays 30, 50. These arrays are separated by an array of power dividers 40 which is associated with the element array 50, another power divider array 20 being associated with the element array 30. Details of implementation of this structure are provided in the last-mentioned copending application.
Previously-known configurations for radiating elements have employed either a patch or slot geometry, wherein circular or rectangular patches or slots, with or without perturbation segments provided thereon, may be provided. While the antennas as disclosed in the three above-mentioned applications have yielded good results over a relatively large bandwidth, the present inventors have discovered that it is possible to provide yet further improvement in performance.